Weld quality control in automated, remote or autonomous welding requires real time monitoring of the weld pool in order to provide sensory feedback from the welded as it is being made. This procedure is analogous to the functions of a human welder as he watches the position and size of the weld pool and, in turn, modifies his positioning of the torch, or varies the welding parameters, to produce a weld structure that accommodates fit-up and distortion induced discrepancies in the welded preparation. In order to provide a useful weld pool viewing system for production welding, a system design must incorporate features that provide a clear view of the weld pool, its local surroundings and its contact with the workpiece while being compactly packaged and positioned relative to the welding torch to minimize physical interference with weld torch access to a confined workpiece configuration, such as the weld seams of a three-surface 90-degree corner arrangement.
The major difficulty encountered in viewing weld pools derives from the severe gradients of light intensity that are developed across the scene in the presence of the welding arc. The brightness of the arc generally either overpowers the average brightness of the weld pool scene leaving the surrounding regions in relative darkness which does not permit the resolution of relevant features by a camera, or overloads the corresponding region of the camera detector causing "blooming" or lateral growth of the high intensity arc region.